Lithographic apparatus and device manufacturing method

ABSTRACT

An immersion lithographic apparatus is disclosed which includes a liquid supply system having an inlet configured to supply a liquid to a space between a projection system of the lithographic apparatus and a substrate and an outlet configured to remove at least part of the liquid, the liquid supply system configured to rotate the inlet, the outlet, or both, about an axis substantially perpendicular to an exposure plane of the substrate.

This is a continuation application of U.S. patent application Ser. No.11/001,082, filed Dec. 2, 2004 now U.S. Pat. No. 7,161,654, which isincorporated by reference herein in its entirety.

FIELD

The present invention relates to a lithographic apparatus and a methodfor manufacturing a device.

BACKGROUND

A lithographic apparatus is a machine that applies a desired patternonto a substrate, usually onto a target portion of the substrate. Alithographic apparatus can be used, for example, in the manufacture ofintegrated circuits (ICs). In that instance, a patterning device, whichis alternatively referred to as a mask or a reticle, may be used togenerate a circuit pattern to be formed on an individual layer of theIC. This pattern can be transferred onto a target portion (e.g.comprising part of, one, or several dies) on a substrate (e.g. a siliconwafer). Transfer of the pattern is typically via imaging onto a layer ofradiation-sensitive material (resist) provided on the substrate. Ingeneral, a single substrate will contain a network of adjacent targetportions that are successively patterned. Known lithographic apparatusinclude so-called steppers, in which each target portion is irradiatedby exposing an entire pattern onto the target portion at one time, andso-called scanners, in which each target portion is irradiated byscanning the pattern through a radiation beam in a given direction (the“scanning”-direction) while synchronously scanning the substrateparallel or anti-parallel to this direction. It is also possible totransfer the pattern from the patterning device to the substrate byimprinting the pattern onto the substrate.

It has been proposed to immerse the substrate in the lithographicprojection apparatus in a liquid having a relatively high refractiveindex, e.g. water, so as to fill a space between the final element ofthe projection system and the substrate. The point of this is to enableimaging of smaller features since the exposure radiation will have ashorter wavelength in the liquid. (The effect of the liquid may also beregarded as increasing the effective numerical aperture (NA) of thesystem and also increasing the depth of focus.) Other immersion liquidshave been proposed, including water with solid particles (e.g. quartz)suspended therein.

However, submersing the substrate or substrate and substrate table in abath of liquid (see for example U.S. Pat. No. 4,509,852, herebyincorporated in its entirety by reference) means that there is a largebody of liquid that must be accelerated during a scanning exposure. Thisrequires additional or more powerful motors and turbulence in the liquidmay lead to undesirable and unpredictable effects.

One of the solutions proposed is for a liquid supply system to provideliquid on only a localized area of the substrate and in between thefinal element of the projection system and the substrate (the substrategenerally has a larger surface area than the final element of theprojection system). One way which has been proposed to arrange for thisis disclosed in PCT patent application no. WO 99/49504, herebyincorporated in its entirety by reference. As illustrated in FIGS. 2 and3, liquid is supplied by at least one inlet IN onto the substrate,preferably along the direction of movement of the substrate relative tothe final element, and is removed by at least one outlet OUT afterhaving passed under the projection system. That is, as the substrate isscanned beneath the element in a −X direction, liquid is supplied at the+X side of the element and taken up at the −X side. FIG. 2 shows thearrangement schematically in which liquid is supplied via inlet IN andis taken up on the other side of the element by outlet OUT which isconnected to a low pressure source. In the illustration of FIG. 2 theliquid is supplied along the direction of movement of the substraterelative to the final element, though this does not need to be the case.Various orientations and numbers of in- and out-lets positioned aroundthe final element are possible, one example is illustrated in FIG. 3 inwhich four sets of an inlet with an outlet on either side are providedin a regular pattern around the final element.

SUMMARY

It would be advantageous, for example, to provide a lithographicapparatus having a liquid supply system wherein a substrate may be movedin different directions without having to switch a flow direction of theliquid between the projection system of the lithographic apparatus and asubstrate.

According to an aspect of the invention, there is provided alithographic apparatus, comprising:

a substrate table configured to hold a substrate;

a projection system configured to project a patterned beam onto a targetportion of the substrate; and

a liquid supply system comprising an inlet configured to supply a liquidto a space between the projection system and the substrate and an outletconfigured to remove at least part of the liquid, the liquid supplysystem configured to rotate the inlet, the outlet, or both, about anaxis substantially perpendicular to an exposure plane of the substrate.

According to an aspect of the invention, there is provided alithographic apparatus, comprising:

a substrate table configured to hold a substrate;

a projection system configured to project a patterned beam onto a targetportion of the substrate; and

a liquid supply system comprising an inlet configured to supply a liquidto a space between the projection system and the substrate and an outletconfigured to remove at least part of the liquid, the liquid supplysystem configured to rotate the inlet and outlet in tandem about an axissubstantially parallel to an optical axis of the projection system inaccordance with a change in movement of the substrate.

According to a further aspect of the invention, there is provided adevice manufacturing method, comprising:

supplying a liquid to a space between a projection system of alithographic apparatus and a substrate;

rotating an inlet configured to supply the liquid to the space, anoutlet configured to remove the liquid, or both, about an axissubstantially perpendicular to an exposure plane of the substrate; and

projecting a patterned beam of radiation, using the projection system,through the liquid onto a target portion of the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich:

FIG. 1 depicts a lithographic apparatus according to an embodiment ofthe invention;

FIGS. 2 and 3 depict a liquid supply system for use in a lithographicprojection apparatus;

FIG. 4 depicts another liquid supply system for use in a lithographicprojection apparatus;

FIG. 5 depicts another liquid supply system for use in a lithographicprojection apparatus;

FIG. 6 depicts a top view of a liquid supply system according to anembodiment of the invention;

FIG. 7 depicts a side view of the liquid supply system of FIG. 6;

FIGS. 8 a to 8 c depict various rotations of a liquid confinementstructure according to an embodiment of the invention; and

FIG. 9 depicts a side view of a liquid supply system according toanother embodiment of the invention.

DETAILED DESCRIPTION

FIG. 1 schematically depicts a lithographic apparatus according to oneembodiment of the invention. The apparatus comprises:

-   -   an illumination system (illuminator) IL configured to condition        a radiation beam PB (e.g. UV radiation or DUV radiation);    -   a support structure (e.g. a mask table) MT constructed to        support a patterning device (e.g. a mask) MA and connected to a        first positioner PM configured to accurately position the        patterning device in accordance with certain parameters;    -   a substrate table (e.g. a wafer table) WT constructed to hold a        substrate (e.g. a resist-coated wafer) W and connected to a        second positioner PW configured to accurately position the        substrate in accordance with certain parameters; and    -   a projection system (e.g. a refractive projection lens system)        PL configured to project a pattern imparted to the radiation        beam PB by patterning device MA onto a target portion C (e.g.        comprising one or more dies) of the substrate W.

The illumination system may include various types of optical components,such as refractive, reflective, magnetic, electromagnetic, electrostaticor other types of optical components, or any combination thereof, fordirecting, shaping, or controlling radiation.

The support structure supports, i.e. bears the weight of, the patterningdevice. It holds the patterning device in a manner that depends on theorientation of the patterning device, the design of the lithographicapparatus, and other conditions, such as for example whether or not thepatterning device is held in a vacuum environment. The support structurecan use mechanical, vacuum, electrostatic or other clamping techniquesto hold the patterning device. The support structure may be a frame or atable, for example, which may be fixed or movable as required. Thesupport structure may ensure that the patterning device is at a desiredposition, for example with respect to the projection system. Any use ofthe terms “reticle” or “mask” herein may be considered synonymous withthe more general term “patterning device.”

The term “patterning device” used herein should be broadly interpretedas referring to any device that can be used to impart a radiation beamwith a pattern in its cross-section such as to create a pattern in atarget portion of the substrate. It should be noted that the patternimparted to the radiation beam may not exactly correspond to the desiredpattern in the target portion of the substrate, for example if thepattern includes phase-shifting features or so called assist features.Generally, the pattern imparted to the radiation beam will correspond toa particular functional layer in a device being created in the targetportion, such as an integrated circuit.

The patterning device may be transmissive or reflective. Examples ofpatterning devices include masks, programmable mirror arrays, andprogrammable LCD panels. Masks are well known in lithography, andinclude mask types such as binary, alternating phase-shift, andattenuated phase-shift, as well as various hybrid mask types. An exampleof a programmable mirror array employs a matrix arrangement of smallmirrors, each of which can be individually tilted so as to reflect anincoming radiation beam in different directions. The tilted mirrorsimpart a pattern in a radiation beam which is reflected by the mirrormatrix.

The term “projection system” used herein should be broadly interpretedas encompassing any type of projection system, including refractive,reflective, catadioptric, magnetic, electromagnetic and electrostaticoptical systems, or any combination thereof, as appropriate for theexposure radiation being used, or for other factors such as the use ofan immersion liquid or the use of a vacuum. Any use of the term“projection lens” herein may be considered as synonymous with the moregeneral term “projection system”.

As here depicted, the apparatus is of a transmissive type (e.g.employing a transmissive mask). Alternatively, the apparatus may be of areflective type (e.g. employing a programmable mirror array of a type asreferred to above, or employing a reflective mask).

The lithographic apparatus may be of a type having two (dual stage) ormore substrate tables (and/or two or more mask tables). In such“multiple stage” machines the additional tables may be used in parallel,or preparatory steps may be carried out on one or more tables while oneor more other tables are being used for exposure.

Referring to FIG. 1, the illuminator IL receives a radiation beam from aradiation source SO. The source and the lithographic apparatus may beseparate entities, for example when the source is an excimer laser. Insuch cases, the source is not considered to form part of thelithographic apparatus and the radiation beam is passed from the sourceSO to the illuminator IL with the aid of a beam delivery system BDcomprising, for example, suitable directing mirrors and/or a beamexpander. In other cases the source may be an integral part of thelithographic apparatus, for example when the source is a mercury lamp.The source SO and the illuminator IL, together with the beam deliverysystem BD if required, may be referred to as a radiation system.

The illuminator IL may comprise an adjuster AD for adjusting the angularintensity distribution of the radiation beam. Generally, at least theouter and/or inner radial extent (commonly referred to as σ-outer andσ-inner, respectively) of the intensity distribution in a pupil plane ofthe illuminator can be adjusted. In addition, the illuminator IL maycomprise various other components, such as an integrator IN and acondenser CO. The illuminator may be used to condition the radiationbeam, to have a desired uniformity and intensity distribution in itscross-section.

The radiation beam PB is incident on the patterning device (e.g., maskMA), which is held on the support structure (e.g., mask table MT), andis patterned by the patterning device. Having traversed the mask MA, theradiation beam PB passes through the projection system PL, which focusesthe beam onto a target portion C of the substrate W. A liquidconfinement structure IH, which is described further below, suppliesimmersion liquid to a space between the final element of the projectionsystem PL and the substrate W.

With the aid of the second positioner PW and position sensor IF (e.g. aninterferometric device, linear encoder or capacitive sensor), thesubstrate table WT can be moved accurately, e.g. so as to positiondifferent target portions C in the path of the radiation beam PB.Similarly, the first positioner PM and another position sensor (which isnot explicitly depicted in FIG. 1) can be used to accurately positionthe mask MA with respect to the path of the radiation beam PB, e.g.after mechanical retrieval from a mask library, or during a scan. Ingeneral, movement of the mask table MT may be realized with the aid of along-stroke module (coarse positioning) and a short-stroke module (finepositioning), which form part of the first positioner PM. Similarly,movement of the substrate table WT may be realized using a long-strokemodule and a short-stroke module, which form part of the secondpositioner PW. In the case of a stepper (as opposed to a scanner) themask table MT may be connected to a short-stroke actuator only, or maybe fixed. Mask MA and substrate W may be aligned using mask alignmentmarks M1, M2 and substrate alignment marks P1, P2. Although thesubstrate alignment marks as illustrated occupy dedicated targetportions, they may be located in spaces between target portions (theseare known as scribe-lane alignment marks). Similarly, in situations inwhich more than one die is provided on the mask MA, the mask alignmentmarks may be located between the dies.

The depicted apparatus could be used in at least one of the followingmodes:

1. In step mode, the mask table MT and the substrate table WT are keptessentially stationary, while an entire pattern imparted to theradiation beam is projected onto a target portion C at one time (i.e. asingle static exposure). The substrate table WT is then shifted in the Xand/or Y direction so that a different target portion C can be exposed.In step mode, the maximum size of the exposure field limits the size ofthe target portion C imaged in a single static exposure.

2. In scan mode, the mask table MT and the substrate table WT arescanned synchronously while a pattern imparted to the radiation beam isprojected onto a target portion C (i.e. a single dynamic exposure). Thevelocity and direction of the substrate table WT relative to the masktable MT may be determined by the (de-)magnification and image reversalcharacteristics of the projection system. In scan mode, the maximum sizeof the exposure field limits the width (in the non-scanning direction)of the target portion in a single dynamic exposure, whereas the lengthof the scanning motion determines the height (in the scanning direction)of the target portion.

3. In another mode, the mask table MT is kept essentially stationaryholding a programmable patterning device, and the substrate table WT ismoved or scanned while a pattern imparted to the radiation beam isprojected onto a target portion C. In this mode, generally a pulsedradiation source is employed and the programmable patterning device isupdated as required after each movement of the substrate table WT or inbetween successive radiation pulses during a scan. This mode ofoperation can be readily applied to maskless lithography that utilizesprogrammable patterning device, such as a programmable mirror array of atype as referred to above.

Combinations and/or variations on the above described modes of use orentirely different modes of use may also be employed.

A further immersion lithography solution with a localized liquid supplysystem is shown in FIG. 4. Liquid is supplied by two groove inlets IN oneither side of the projection system PL and is removed by a plurality ofdiscrete outlets OUT arranged radially outwardly of the inlets IN. Theinlets IN and OUT can be arranged in a liquid confinement structure,such as plate with a hole in its center, through which the projectionbeam is projected. Liquid is supplied by one groove inlet IN on one sideof the projection system and removed by a plurality of discrete outletsOUT on the other side of the projection system, causing a flow of a thinfilm of liquid between the projection system and the substrate. Thechoice of which combination of inlet IN and outlets OUT to use candepend on the direction of movement of the substrate (the othercombination of inlet IN and outlets OUT being inactive).

Another immersion lithography solution with a localized liquid supplysystem solution which has been proposed is to provide the liquid supplysystem with a liquid confinement structure which extends along at leasta part of a boundary of the space between the final element of theprojection system and the substrate table. Such a solution isschematically illustrated in FIG. 5. The liquid confinement structure issubstantially stationary relative to the projection system in the X-Yplane though there may be some relative movement in the Z direction (inthe direction of the optical axis). A seal is formed between the liquidconfinement structure and the surface of the substrate.

Referring to FIG. 5, reservoir 10 forms a contactless seal to thesubstrate around the image field of the projection system so that liquidis confined to fill a space between the substrate surface and the finalelement of the projection system. The reservoir is formed by a liquidconfinement structure 12 positioned below and surrounding the finalelement of the projection system PL. Liquid is brought into the spacebelow the projection system and within the liquid confinement structure.The liquid confinement structure extends a little above the finalelement of the projection system and the liquid level rises above thefinal element so that a buffer of liquid is provided. The liquidconfinement structure has an inner periphery that at the upper end, inan embodiment, closely conforms to the shape of the projection system orthe final element thereof and may, e.g., be round. At the bottom, theinner periphery closely conforms to the shape of the image field, e.g.,rectangular though this need not be the case.

The liquid is confined in the reservoir by a gas seal 16 between thebottom of the liquid confinement structure and the surface of thesubstrate W. The gas seal is formed by gas, e.g. air, synthetic air, N₂or an inert gas, provided under pressure via inlet 15 to the gap betweenliquid confinement structure 12 and substrate and extracted via firstoutlet 14. The overpressure on the inlet 15, vacuum level on the firstoutlet 14 and geometry of the gap are arranged so that there is ahigh-velocity gas flow inwards that confines the liquid. Such a systemis disclosed in U.S. patent application Ser. No. 10/705,783, herebyincorporated in its entirety by reference.

In the liquid confinement structure of FIG. 5, liquid may supplied toand/or removed from the space between the projection system and thesubstrate/substrate table by port 13. In an embodiment, port 13comprises a pair of inlets 13 (for example, on opposite sides of anexposure field) which supply liquid to the space. The liquid supplied bythe inlet(s) 13 may be removed by outlet 14 which surrounds a peripheryof the exposure field (as used herein, exposure field includes not onlyan area through which the projection beam passes but additionally oralternatively may include an area through which measurement, by for ameasurement radiation beam, may be taken). Due to the outlet 14, liquidis confined to the space and within the exposure field irrespective ofthe direction of movement of the substrate/substrate table. A liquidflow may be established and/or maintained in the space throughappropriate configuration of inlet(s) 13 and outlet 14. However, whereonly seal 16 is used, liquid supplied by inlet(s) to the space andwithin the exposure field may only just be maintained therein without aliquid flow in the space.

In an embodiment, port 13 comprises an inlet and an outlet (for example,on opposite sides of an exposure field). The seal 16, which surrounds anexposure field, confines the liquid to the space and within the exposurefield without a need for a liquid outlet. Where a flow of liquid throughthe space is desired, the inlet/outlet 13 may be appropriatelyconfigured to establish and/or maintain the flow.

In an embodiment, the port 13 extends around a periphery of an exposurefield and thus provides a rotationally symmetric liquid inlet. Whereport 13 only includes an inlet, outlet 14 may be provided around aperiphery of an exposure field to contain liquid therein during movementof the substrate/substrate table in any direction. Additionally oralternatively, seal 16 provided around a periphery of an exposure fieldmay contain liquid in the exposure field during movement of thesubstrate/substrate table in any direction. And, where port 13 furtherincludes an outlet and a liquid flow is established between the inletand outlet of port 13, seal 16 provided around a periphery of anexposure field may contain liquid in the exposure field during movementof the substrate/substrate table in any direction.

Thus, with the liquid supply system of FIG. 5, liquid is confined to thespace between the projection system and the substrate/substrate tableand within the exposure field without the need for turning off or onparticular inlet(s) and/or outlet(s) or without depending on a directionof movement of the substrate/substrate table.

Referring to FIGS. 6 and 7, a top view and a side view, respectively, ofa liquid supply system according to an embodiment of the invention areschematically depicted. The liquid supply system comprises a liquidconfinement structure 20 configured to at least partially confine aliquid to a space 22 between the projection system and the substrate Wand/or substrate table WT. The liquid confinement structure 20 comprisesan inlet 24 configured to supply liquid to the space and an outlet 26configured to remove the liquid. The substrate/substrate table movesrelative to the liquid confinement structure (and the projection system)in an X-Y plane substantially parallel to a plane of the liquidconfinement structure. In FIGS. 6 and 7, arrows 28 (e.g., in the Xdirection) depict one example of this movement, although as will beapparent the substrate/substrate table may move in other directions(including rotations)

The liquid confinement structure is connected to a base or the ground(not shown) via a frame 30. In an embodiment, the projection system isconnected to a different frame (not shown) from the liquid confinementstructure so that the projection system and the liquid confinementstructure are mechanically isolated such that transmission of vibrationsand forces between the projection system and the liquid confinementstructure is minimized or reduced. The different frame for theprojection system may also be connected to the base or ground or mayconnected to, but isolated from, the frame for the liquid confinementstructure. The liquid confinement structure is substantially stationaryin the X and Y directions and may move in the Z direction. In FIG. 6, atop portion of the projection system (seen, for example, in FIG. 7) isomitted so the liquid confinement structure can be clearly seen.

In an embodiment, like the liquid supply system in FIGS. 2, 3 and 4, themovement of the substrate W/substrate table WT facilitates confinementand distribution of the liquid in the space and within an exposurefield. In particular, liquid is supplied by the inlet to the space atone side of the exposure field and movement of the substrate/substratetable facilitates distribution of the liquid in the exposure field andto the outlet on an opposite side of the exposure field. Thus, theprojection system and the liquid confinement structure provideconfinement for a top of the space, the substrate/substrate tableprovide confinement for a bottom of the space, and the inlet and outleton opposite sides of an exposure field in combination with movement ofthe substrate/substrate table in a direction from the inlet to theoutlet provide distribution and confinement laterally within the space.The combination of the movement of the substrate/substrate table andpositioning of the inlet and outlet on opposite sides of the exposurefield facilitates to establish and maintain a flow of a thin film ofliquid in the space. The arrows 32 (e.g., extending in the X direction)depict an example of the flow of the liquid in the space although aswill be apparent the flow of liquid may move in other directions(including rotations) depending on the positioning of the inlet andoutlet and the movement of the substrate/substrate table.

In the supply systems of FIG. 2, 3 and 4, where there is a change indirection of movement of the substrate/substrate table, confinement anddistribution of the liquid in the space and within an exposure field isfacilitated by activating/deactivating one or more particular inlet andoutlets on or outside a periphery of the exposure field. For example, inthe case of FIGS. 2, 3 and 4, a first inlet IN on one side of theexposure field supplies liquid to the space and a first outlet OUT onanother side of the exposure field when the substrate/substrate tablemoves in a first direction from the first inlet IN towards the secondoutlet OUT. Where the substrate/substrate table moves in a seconddirection 180° to the first direction, a second inlet IN and a secondoutlet OUT are activated and the first inlet IN and second outlet OUTare deactivated. The second inlet IN is positioned at a positionopposite to the first inlet IN (adjacent the first outlet OUT) and thesecond outlet OUT is positioned at a position opposite to the firstoutlet OUT (adjacent the first inlet IN). Thus, in this configuration,the second direction of the substrate/substrate table is from the secondinlet IN towards the second outlet OUT. In an embodiment, the firstinlet IN may be switched into the second outlet OUT, for example, byswitching from a liquid source to a low pressure source, and the firstoutlet OUT may be switched into the second inlet IN, for example, byswitching from a low pressure source to a liquid supply. Inlets andoutlets may also be provided for movements of the substrate/substratetable in other directions (see, for example, FIG. 3). Thus, the liquidsupply systems of FIGS. 2, 3 and 4 employ a non-rotationally symmetricliquid inlet and outlet system leading to the switching of liquid inletand outlet positions on or outside the periphery of the exposure fielddepending on substrate/substrate table movement (e.g., in a scandirection) through activation/deactivation of one or more liquid inletsand outlets.

In an embodiment, switching of liquid inlet and outlet positions throughactivation/deactivation of one or more liquid inlets and outlets may beavoided where one or more inlets and/or outlets are rotated around anaxis substantially perpendicular to an exposure plane of the substrate,e.g., the Z axis or an optical axis of the projection system. Referringto FIGS. 6 and 7, one or more motors 34 rotate the liquid confinementstructure, comprising the inlet and outlet, relative to the frame andabout the axis, thus moving both the inlet and outlet in tandem. Thecurved arrows 38 show how the liquid confinement structure rotates. Acontroller 40 controls the motor(s) based upon a direction of movementof the substrate/substrate table. In particular, the controller controlsthe motor(s) so that the liquid confinement structure is positioned sothat a direction from the inlet to the outlet is substantially paralleland in the same direction as the movement of the substrate/substratetable. In this way, the inlet and outlet need not beactivated/deactivated as the liquid confinement structure rotates with achange in the movement of the substrate/substrate table to keep theliquid confined in the space between the projection system and thesubstrate/substrate table and the flow of liquid in the space in thesame direction as the movement of the substrate/substrate table. Withappropriate rotation of the inlet and outlet, the movement of thesubstrate/substrate table may automatically transport the liquid fromthe inlet to the outlet in all directions of movement of thesubstrate/substrate table. The controller may operated in a feed-forwardor feedback manner.

In an embodiment, the liquid supply system is configured to rotate theinlet, the outlet, or both, about an axis substantially perpendicular toan exposure plane of the substrate. While the liquid supply system maybe able to provide all these rotating functions, in embodiments, theliquid supply system may provide rotation of only the inlet (without theability to rotate the outlet) or rotation of only the outlet (withoutthe ability to rotate the inlet) or rotation of both the inlet oroutlet. In other words, a liquid supply system need not be able toprovide all these rotation capabilities but rather may provide only onetype of rotation capability.

Referring to FIGS. 8 a to 8 c, the liquid confinement structure is shownschematically at different rotations to explain the operation of theliquid supply system according to an embodiment of the invention. Inthis example, however, the liquid confinement structure is connected tothe projection system (or a frame supporting the projection system)without the use of a frame as depicted in FIGS. 4 and 5. In this case,one or more motors (not shown) move the liquid confinement structurerelative to the projection system about an axis substantially parallelto the optical axis of the projection system. Transmission of vibrationsand/or forces between the liquid confinement structure and theprojection system may be reduced or avoided through the use of anisolator or a damping mechanism. The rotation of this exemplary liquidconfinement structure is substantially similar to the rotation of theexemplary liquid confinement structure in FIGS. 4 and 5.

Referring to FIG. 8 a, the liquid confinement structure is positioned sothat a direction from the inlet to the outlet of the liquid confinementstructure (represented by arrows) is substantially parallel to and inthe same direction as the movement of the substrate/substrate table(represented by arrow). In FIG. 8 a, the movement of thesubstrate/substrate table is in a scanning direction. When the movementof the substrate/substrate table changes to, for example, a steppingdirection as shown in FIG. 8 b, the liquid confinement structure isrotated about 90 degrees in the clockwise direction so that thedirection from the inlet to the outlet of the liquid confinementstructure (represented by arrows) is substantially parallel to and inthe same direction as the movement of the substrate/substrate table(represented by arrow). When the movement of the substrate/substratetable changes again to, for example, a scanning direction again(although having an opposite sign to the scanning direction in FIG. 8 a)as shown in FIG. 8 c, the liquid confinement structure is rotated about90 degrees further in the clockwise direction so that the direction fromthe inlet to the outlet of the liquid confinement structure (representedby arrows) is substantially parallel to and in the same direction as themovement of the substrate/substrate table (represented by arrow). If themovement of the substrate/substrate table changed again to, for example,a stepping direction such as shown in FIG. 8 b, the liquid confinementstructure need only be rotated about 90 degrees in the counterclockwisedirection so that the direction from the inlet to the outlet of theliquid confinement structure (represented by arrows) is substantiallyparallel to and in the same direction as the movement of thesubstrate/substrate table (represented by arrow). Thus, while the one ormore inlets and/or outlets may be rotated to any angle in an embodiment(e.g., 0 to 360 degrees), the one or more inlets and/or outlets may berotated only within the range from 0 to 200 degrees.

In an embodiment, the one or more inlets and/or outlets may be rotatedonly to positions where the direction from the inlet to the outlet ofthe liquid confinement structure is substantially parallel to and in thesame direction as the scanning movement of the substrate/substratetable. In this case, only a limited number of rotations may be needed.

In an embodiment, instead of the liquid confinement structure beingrotated, an individual inlet and/or outlet or a group of inlets and/oroutlets may rotated within the liquid confinement structure itself. Forexample, where an outlet is provided around a periphery of an exposurefield, it may be advantageous simply to rotate one or more inlets aroundall or a part of the periphery of the exposure field.

While one or more motors were described above to rotate the liquidconfinement structure or the one or more inlets and/or outlets, almostany movement mechanism may be used. The motor(s) may be one or morelinear motors or one or more mechanical actuators. The frame and/orliquid confinement structure may comprise a track to guide the rotationof the one or more inlets and/or outlets or the liquid confinementstructure. One or more appropriate bearings may be provided.

Rotation of one or more of the inlets and/or outlets has an advantage ofavoiding activating/deactivating one or more inlets and/or outlets. Suchactivation/deactivation may have deleterious effects to the liquidquality. For example, valves in the liquid supply system may becontaminated and so introduce contamination in the liquid when liquidinlet and outlet positions are switched through activation/deactivationof one or more inlets and/or outlets. Changing the direction of orstopping the flow of liquid through particle filters and/or de-bubblersmay cause introduction of contamination and/or bubbles when switchingliquid inlet and outlet positions through activation/deactivation of oneor more inlets and/or outlets. Further, where a liquid supply system hasa single liquid inlet and a single liquid outlet or an inlet/outletcombination at each of two opposing positions (such as for example asshown in FIG. 4), rotation may help to avoid or reduce liquid leakage incertain substrate/substrate table movement directions, for example, in adirection perpendicular to the line between the single liquid inlet andthe single liquid outlet or perpendicular to the line between the inletsoutlet combinations at opposing positions. Further, rotation may help toavoid or reduce deleterious vibrations in the lithographic apparatuscaused by activation/deactivation of one or more inlets and/or outlets.

In an embodiment, the inlet, the outlet, or both may be rotated so as tomaintain the flow of liquid in a direction substantially perpendicularto a direction of movement of the substrate. To maintain the liquid inthe exposure field, a seal or outlet is provided around the periphery ofthe exposure field to contain or remove liquid as movement of thesubstrate perpendicular to the direction of the flow of the liquid inthe exposure field may draw the liquid out of the exposure field (asdistinct from a flow of liquid in the same direction as a direction ofmovement of the substrate in which case surface tension could keep theliquid substantially in the exposure field) and out to portions of theapparatus where liquid is undesirable. Referring to FIG. 9, the liquidsupply system of this embodiment is substantially the same as shown inFIG. 7 except that an outlet 42 is provided around a periphery of theexposure field to remove liquid that may escape from the exposure field.Depending on the configuration of the liquid supply system, the flow ofliquid and/or the movement of the substrate, the outlet 42 need notfully surround the exposure field.

In an embodiment, the inlet, the outlet, or both may rotated so as tomaintain the flow of liquid, at different times or points, in adirection substantially perpendicular to a direction of movement of thesubstrate or in a direction substantially parallel to a direction ofmovement of the substrate.

In a twin or dual stage immersion lithography apparatus, two tables areprovided for respectively supporting a substrate. Leveling measurementsare carried out with a table at a first position, without immersionliquid, and exposure is carried out with a table at a second position,where immersion liquid is present. Alternatively, the apparatus has onlyone table and moves between separate leveling and exposure positions.

Although specific reference may be made in this text to the use oflithographic apparatus in the manufacture of ICs, it should beunderstood that the lithographic apparatus described herein may haveother applications, such as the manufacture of integrated opticalsystems, guidance and detection patterns for magnetic domain memories,flat-panel displays, liquid-crystal displays (LCDs), thin-film magneticheads, etc. The skilled artisan will appreciate that, in the context ofsuch alternative applications, any use of the terms “wafer” or “die”herein may be considered as synonymous with the more general terms“substrate” or “target portion”, respectively. The substrate referred toherein may be processed, before or after exposure, in for example atrack (a tool that typically applies a layer of resist to a substrateand develops the exposed resist), a metrology tool and/or an inspectiontool. Where applicable, the disclosure herein may be applied to such andother substrate processing tools. Further, the substrate may beprocessed more than once, for example in order to create a multi-layerIC, so that the term substrate used herein may also refer to a substratethat already contains multiple processed layers.

The terms “radiation” and “beam” used herein encompass all types ofelectromagnetic radiation, including ultraviolet (UV) radiation (e.g.having a wavelength of or about 365, 248, 193, 157 or 126 nm).

The term “lens”, where the context allows, may refer to any one orcombination of various types of optical components, including refractiveand reflective optical components.

While specific embodiments of the invention have been described above,it will be appreciated that the invention may be practiced otherwisethan as described. For example, where applicable, the invention may takethe form of a computer program containing one or more sequences ofmachine-readable instructions describing a method as disclosed above, ora data storage medium (e.g. semiconductor memory, magnetic or opticaldisk) having such a computer program stored therein.

One or more embodiments of the present invention may be applied to anyimmersion lithography apparatus, in particular, but not exclusively,those types mentioned above. A liquid supply system is any mechanismthat provides a liquid to a space between the projection system and thesubstrate and/or substrate table. It may comprise any combination of oneor more structures, one or more liquid inlets, one or more gas inlets,one or more gas outlets, and/or one or more liquid outlets, thecombination providing and confining the liquid to the space. In anembodiment, a surface of the space may be limited to a portion of thesubstrate and/or substrate table, a surface of the space may completelycover a surface of the substrate and/or substrate table, or the spacemay envelop the substrate and/or substrate table.

The immersion liquid used in the apparatus may have differentcompositions, according to the desired properties and the wavelength ofexposure radiation used. For an exposure wavelength of 193 nm, ultrapure water or water-based compositions may be used and for this reasonthe immersion liquid is sometimes referred to as water and water-relatedterms such as hydrophilic, hydrophobic, humidity, etc. may be used.

The descriptions above are intended to be illustrative, not limiting.Thus, it will be apparent to one skilled in the art that modificationsmay be made to the invention as described without departing from thescope of the claims set out below.

1. A lithographic apparatus, comprising: a substrate table configured tohold a substrate; a projection system configured to project a patternedbeam onto a target portion of the substrate; and a liquid supply systemcomprising an inlet configured to supply a liquid to a space between theprojection system and the substrate and an outlet configured to removeat least part of the liquid, the liquid supply system configured torotate the inlet, the outlet, or both, about an axis substantiallyperpendicular to an exposure plane of the substrate.
 2. The apparatusaccording to claim 1, wherein the liquid supply system comprises aliquid confinement structure configured to at least partly confine theliquid in the space, the liquid confinement structure comprising theinlet and the outlet and configured to rotate about the axis.
 3. Theapparatus according to claim 2, wherein the inlet and outlet arerespectively positioned on opposite sides of an exposure field throughwhich the patterned beam is to be projected.
 4. The apparatus accordingto claim 2, wherein the liquid confinement structure is supported on aframe connected to a base of the apparatus or ground and the liquidsupply system comprises a motor configured to rotate the liquidconfinement structure relative to the frame.
 5. The apparatus accordingto claim 1, wherein, in use, a direction of flow of the liquid in thespace substantially corresponds to a direction of movement of thesubstrate.
 6. The apparatus according to claim 5, wherein, in use, thedirection of the flow of the liquid in the space substantiallycorresponds to a direction of scanning movement of the substrate.
 7. Theapparatus according to claim 1, comprising a controller configured tomaintain, through rotation of the inlet, the outlet, or both, adirection of flow of the liquid in the space to substantially correspondto the direction of movement of the substrate whenever the substrate ismoved.
 8. The apparatus according to claim 1, wherein the inlet, theoutlet, or both, are configured to be rotated less than or equal to 360degrees.
 9. The apparatus according to claim 1, wherein the inlet, theoutlet, or both, are configured to be rotated less than or equal to 200degrees.
 10. The apparatus according to claim 1, wherein the controlleris configured to rotate the inlet, the outlet, or both only to positionswhere a direction from the inlet to the outlet is substantially parallelto and in the same direction as a scanning movement of the substrate.11. The apparatus according to claim 1, comprising a motor configured torotate the inlet, the outlet, or both, in a counterclockwise directionand a clockwise direction about the axis.
 12. The apparatus according toclaim 1, wherein the liquid supply system comprises a plurality ofinlets, a plurality of outlets, or both and is configured to rotate theinlets, the outlets, or both.
 13. The apparatus according to claim 1,wherein, in use, a direction of flow of the liquid in the space issubstantially perpendicular to a direction of movement of the substrate.14. The apparatus according to claim 1, wherein the liquid supply systemis configured to rotate the inlet only about an axis substantiallyperpendicular to an exposure plane of the substrate.
 15. The apparatusaccording to claim 1, wherein the liquid supply system is configured torotate the outlet only about an axis substantially perpendicular to anexposure plane of the substrate.
 16. The apparatus according to claim 1,wherein the liquid supply system is configured to rotate the inlet andoutlet about an axis substantially perpendicular to an exposure plane ofthe substrate.
 17. A lithographic apparatus, comprising: a substratetable configured to hold a substrate; a projection system configured toproject a patterned beam onto a target portion of the substrate; and aliquid supply system comprising an inlet configured to supply a liquidto a space between the projection system and the substrate and an outletconfigured to remove at least part of the liquid, the liquid supplysystem configured to rotate the inlet and outlet in tandem about an axissubstantially parallel to an optical axis of the projection system inaccordance with a change in movement of the substrate.
 18. The apparatusaccording to claim 17, wherein the inlet and the outlet are configuredto be rotated less than or equal to 200 degrees.
 19. The apparatusaccording to claim 17, wherein, in use, a direction of flow of theliquid in the space is substantially perpendicular to a direction ofmovement of the substrate.
 20. The apparatus according to claim 17,wherein the liquid supply system comprises a plurality of inlets, aplurality of outlets, or both and is configured to rotate the inlets,the outlets, or both.